1. Field of the Invention
This invention is directed to a method and apparatus for the production of useful materials from fine particulate substances whose components include matter deemed undesirable in the final product.
2. Description of the Prior Art
Practically all natural materials contained in the earth's crust which have proven beneficial to mankind exist in less than the pure or desired state so means have been developed over the years to retrieve the wanted substance. Examples are: fractional distillation of crude oil; smelting of ores; selecting, crushing and screening of minerals; washing of sand; and some of the newer flotation techniques where desirable elements are brought to the top of a bath vessel and skimmed from the surface. Most of the physical processes require preparation of one sort or another to obtain a generally suitable size consist which will favor separation of fractions based on the weight of the fraction component particles. In short, we concern ourselves with substance specific gravity or its relationship to the weight of water in a one cubic foot volume which is 62.4 pounds. The closer the size similarity among different substances, the more pronounced will be the effect of specific gravity or different substance particle weight in any separation attempt. To further early substance separation "sharpness", it was found agitation of the bath was helpful. A crude example is panning for gold where silt and sand can be kept in a water suspension in the much heavier precious metal sinks. The bath is poured off leaving the gold in the pan. The next step was to increase the specific gravity of the bath by means of sand, clay, calcium chloride and the present generally used magnetite additions. This permitted accurate control of the amount of unwanted material contained in a unit of desired substance. Generally speaking, this is the present condition of large commercial beneficiation installations today. Various devices such as dense medium vessels, water cyclones and froth flotation cells are innovations and all embody one or more of the aforementioned basic principles in the physical beneficiation of natural materials processes.
Past exploitation of saleable earth extractions proved successful generally when the initial deposit was of good quality as improvement techniques were crude; hand mining and only being paid for quality material; picking tables and belts for visual and physical rejection of unwanted material and what seemed to be an endless reserve of raw material. Consequently, a great deal of easily extractable ores, coal, masonry rock and amorphous substances, all of the highest quality, were removed. The advent of mechanical extraction, which is nonselective produces undesirable material along with the desired. Environmental mandates now place constraints as to subsequent consumption of many substances, the result of which is many basic industries concerned with the extraction of natural resources find their present posture somewhat uncomfortable.
One objective of this invention concerns itself, but is not limited to, the beneficiation of bituminous coal. Coal extraction is a specific example of the brief description of a basic natural resource industry which is considered vital to the national interest, but is hampered in its functioning as such because of a combination of circumstances which would seem insurmountable at this writing. When one winnows and sifts the millions of words written and spoken as to coal utilization in the United States today and why it is not solving our national energy oil dependence there is but one answer, sulfur dioxide in the combustion emmissions. The allowable amount is 1.2 pounds of SO.sub.2 per million btus., of coal combusted which translates to about 0.5 of 1% of elemental sulfur by weight, per ton of coal. The Sulfur mainly is contained as a component of iron pyrites and also as an organic substance within the coal structure. One objective of this invention is removal of pyritic Sulfur during coal preparation and containment of SO.sub.2 emissions during the coal subsequent heating and combustion.